There are various techniques for separating and extracting sound from a specific sound source from an audio signal in which a plurality of sound sources are mixed. For example, there is a technique that identifies the direction of a sound source by performing independent component analysis on multiple input signals from a microphone array, thereby separating the sound source. There are many literatures regarding this technique, such as one aimed at improving accuracy and one in which the way of reducing the amount of calculation is improved (for example, Patent Literature 1 below).